RE: SSTC hits 66"

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: jimmy hynes <chunkyboy86-at-yahoo-dot-com> 

Hey,

Comments interspersed.
--- Tesla list <tesla-at-pupman-dot-com> wrote:
 > Original poster: "Steve Conner" <steve.conner-at-optosci-dot-com>
 >
 >  >If I didn't want Steve W. to succeed, I would have suggested
 >  >adding a series
 >  >resistor instead of capacitor :-P
 >
 > ROTFLMAO :D but would Steve have fallen for it...

Well, probably not the series resistor part :P. Steve will correct me if 
I'm wrong, but I think
what happened is I kept bugging him to throw in a series resonant cap, but 
he had already done
that without knowing it. His DC blocking cap was resonating with his low 
inductance primary then.
That was when he was still using MOSFETS :P
 >
 >  >Maybe we should find a way to work together and build an electrum sized
 >  >coil :-)
 >
 > Don't laugh... I reckon it is possible in theory to build a DRSSTC or OLTC
 > of that size. And some mad b*****d will do it sooner or later.

It was a smiley face, as in "that would be cool", not laughing. So now :-P 
to you ;-)
I think it would be tough to get all us SS guys to one spot so we could do 
it together though :-(

 >In fact I
 > heard that Greg Leyh had decided to build his ALF monster twin coil as an
 > OLTC, using banks of 6.6kV 3000A IGBTs or similar. I suppose the "line" he's
 > running "off" would be a 12kV three-phase feeder ::)

Steve Ward told me that the ALF thing was going to be solid state, and that 
he was going to build
a big twin prototype. I didn't believe him at first ;-). I got Dan Strother 
to email Greg about
that thing, and Greg confirmed it. That would be awesome if it was ever made.

 > Nobody knows what topology will be best for the really big coils. The 6.6kV
 > 3000A bricks are probably too slow for a DRSSTC, but an OLTC has less speed
 > requirements so might still be able to use them. The smaller, faster bricks
 > could be assembled into an array for a DRSSTC, but this can only be made so
 > big before current sharing becomes a problem.
 >

The a big OLTC would definatly need a high input voltage. Your coil is at 
the impedance matching
limit for 1kv. Hard to go much less than 1 turn :P.

If the coil was big, the frequency would be lower, so they might be fast 
enough. Besides, the
switching loss can be pretty bad before you get less sparks/IGBT than an 
OLTC ;-). Depending on
the site power, it might be a good idea to use the topology Steve Ward used 
in his SSSSTC. A
SSDRSSTC?

 > Having said this, I reckon the DRSSTC is extensible to 10-15 foot arcs,
 > using a full bridge of four CM600 type bricks, careful low impedance
 > construction, and a 600V DC bus (derived from rectified 3-phase 480V line,
 > or failing that, from 240 single phase through a boost converter PFC) with a
 > massive low impedance electrolytic cap bank.

Steve Ward is planning on doing a 15 footer based on his ISSTC design, and 
I have thought out how
to do the low impedance construction, but haven't decided to do it yet.

 > I think the main obstacles are cost of film/electrolytic cap banks,
 > shielding the drive circuits from the colossal E-M fields, space for testing
 > it, power supply (not everyone has a 32A 3-phase service, or a 15kW boost
 > converter) and getting it all to work without blowing out 20 sets of bricks
 > :(

I think I pretty much agree with this. I think I can probably get most of 
that, but I am not sure
about the space part :-/

Terry, thanks for starting all of this! We still want to see your OLTC on 240!

=====
Jimmy